U. Ripamonti et al., IMMEDIATE RECONSTRUCTION OF MASSIVE CRANIO-ORBITO-FACIAL DEFECTS WITHALLOGENEIC AND ALLOPLASTIC MATRICES IN BABOONS, Journal of cranio-maxillo-facial surgery, 21(7), 1993, pp. 302-308
40 cranio-orbito-facial osseous defects were created in 20 adult male
baboons (Papio ursinus) to test the effectiveness of an allogeneic and
an alloplastic matrix implant for the functional and morphological re
pair of the disassembled craniofacial complex. In each animal, one def
ect was reconstructed with a craniofacial bone segment harvested from
donor adult baboons, and processed so as to obtain autolysed antigen-e
xtracted allogeneic (AAA) bone matrix, preserving the bone morphogenet
ic protein (BMP) activity essential for bone induction. The contralate
ral defect was implanted with spherical macrobeads of polymethylmethac
rylate (PMMA) coated with poly-2-hydroxyethylmethacrylate (PHEMA), and
sintered into a porous molded implant, replicating the structural ana
tomy of the avulsed osseous segment. Histological analysis was carried
out on undecalcified and decalcified bone sections prepared from spec
imens harvested at 3, 6 and 12 months after surgery. In AAA bone, the
morphogenetic response was characterized by vascular invasion and mese
nchymal cell aggregation after partial resorption of the implanted mat
rix. This was followed by bone deposition at the osteotomy interfaces
and within the medullary spaces of the implanted AAA bone. Although bo
ne ingrowth did occur in some PMMA/PHEMA specimens, the majority of im
plants showed fibrous union at the recipient interfaces. The limited b
one ingrowth may be related to narrow interconnections between larger
porous spaces after chemical synthesis of the two polymeric components
. Osteogenesis in AAA bone appeared consistent with osteoconductive in
vasion from the viable bone at the recipient interfaces. In addition,
the finding of a delicate trabecular-like bone, appositional to the ce
ntral areas of the implanted matrix, suggests bone formation by induct
ion.